20X TBS, pH 7.4 is a Tris-buffered saline concentrate of 400 mM Tris and 3 M sodium chloride in purified water. Dilution to 1X gives 20 mM Tris and 150 mM sodium chloride at pH 7.4. The 1 L fill makes 20 L of 1X buffer.

It is commonly used to prepare large volumes of Tris-buffered saline for immunoassays, western blotting, and protein purification, where the concentrate reduces storage and handling volume. Dilute 50 mL to 1 L with purified water for 1X, and verify pH after dilution.